RAR is a general purpose archiving and compression program competing with/replacing programs such as PKZip, ARJ, and others. RAR offers significantly improved compression ratios, easier use and a cheaper price as well as supporting long file names, disk spanning, and self-extracting file creation.

Changes in Current Version:
Now Explorer context menu contains "Convert" and "Test" items
Bugs fixed
More info:
hxxp://www.rarlab.com/

I tested WinRAR 3.20 Beta 2 and doesn't work 100%.